1. Field of the Invention
The invention relates to a sheeting device for supporting the walls of a trench with a stepped cross section, and more particularly to a sheeting device having pairs of plates that are guided on and held in place by columns.
2. Description of Related Art
A conventional sheeting device is disclosed, for example, in European Patent No. 0 100 083 of the present applicant. The known sheeting device has a guide plane formed by a wall of the column that is located in the interior of the trench against which the marginal areas of a pair of plates (i.e., trench liners) abut. A lower and inner plate is made slightly shorter than an upper and outer plate. At the edge of the upper and outer plates, a projecting supporting edge is formed that is directed inward and that fits around the marginal area of the lower inner plate so that the edges of both plates rest on the guide plane next to one another. The advantage of these sheeting devices lies in the simple and open design of a single guide channel to receive the edges of the inner and outer plates.
In order for the marginal area of the outer plate to fit around the marginal area of the inner plate, the outer plates are provided with supporting edges that project inward. The production of these supporting edges that project and are located on both sides of an outer plate is labor and cost intensive. In addition, these projecting supporting edges can easily be damaged during loading, transport, and unloading of the plates as well as during assembly of the sheeting device. Finally, stacked outer plates take up an unnecessarily large volume of space.
It is desirable to provide a sheeting device that makes it possible to support both plates in a single guide channel without the marginal area of one plate having to fit around a marginal area of another plate.